Originally Posted by oct1949

Over the yrs of researching and learing, Here are some numbers I've found and keep..


Info the CFM's of different Air filter and how much there Air Flow is


HD stock - 171CFM
Stage 1 Big Sucker - 200CFM
Stage 2 Big Sucker - 250CFM
Kuryakyn Twin Velocity - 270CFM
E-3014 = 248 CFM RK-3009 kit
E-3037 = 301 CFM RK-3910 kit
HD-0800 = 231 CFM SE replacement
Doherty Powerpacc - 287CFM
SE Air Cleaner - 287 CFM
Zippers - 321 CFM
Woods Carbs - 4 models 235CFM upto 340CFM
BC Overflow - 800+CFM


Your actual need is (103 X 5800 X .9 divided by 3456 = about 155 CFM) is what your engine will flow and need..

So if you keep you filter clean,,, anything over 250 CFM will/ should be plenty on stock heads and cams 103..
I went with SE/AC and it works well with my cams and no head work, i did buy a Real K&N filter for it,, Not the HD filter made by K&N,, they are not the same

Thinking just get the one that rings your bell and then make sure it has enough flow..